The invention relates to a universal joint for a cardan shaft suitable for transmitting high torques, having two joint yokes, each of which is connected to two trunnions of a trunnion cross, having the following features:
(a) each joint yoke comprises a single part, i.e. one joint yoke hub and two yoke eyes together form an integral component;
(b) each trunnion of the trunnion cross is mounted by means of a radial bearing and by means of an axial bearing separate therefrom in the assigned yoke eye, which is provided with a bearing cover; and
(c) the axial bearing is located between the end face of the trunnion and the bearing cover, which (directly or indirectly) rests on a supporting surface of the yoke eye facing away from the axis of rotation of the cardan shaft. A universal joint of this generic type is known from German Patent No. 2,625,960 (British Patent No. 1,539,497).
When cardan shafts of this type are used in heavy engineering, the joints are exposed, depending on the individual case, not only to high torques but also, to a substantial degree, to transverse forces. The universal joints are therefore equipped not only with radial bearings, which serve primarily to transmit the peripheral forces, but also with axial bearings to absorb the transverse forces and to adjust the transverse play within the joint. The transverse forces are transmitted from the trunnion cross to the joint yoke, or vice versa, by way of the roller bearing rings concerned, which have to be axially secured in the receiving hole in the joint yoke, this securing being fully subjected to the transverse force.
It is known from German Patent No. 2,625,960 that the transverse forces acting in the longitudinal axis of the trunnion can be passed directly from the end face of the trunnion into the bearing cover. The possibility then exists of passing the transverse force either via screws into the yoke or via a securing ring which is inserted in grooves within the bearing hole. The securing rings, however, are often inadequate to accommodate the loads arising in heavy engineering, and are forced out of the groove, which results in destruction of the bearing.
Attempts have therefore been made to pass the transverse force from the region of the trunnion root, in other words the transition zone between two adjacent trunnions, onto a radial bearing outer ring provided with a collar into the joint yoke (German Utility Model No. 1,858,494). To do this, however, either the outer ring must be inserted before the assembly of the trunnion cross, or the bearing eye with the bearing hole in the joint yoke must be of two-part design. The latter measure entails substantial weakening of the joint and of the trunnion cross in the region of the trunnion root, since this arrangement of the axial bearing in the region of the trunnion root occupies precisely that structural space which is necessary for a robust design of the trunnion cross.
In all solutions described hitherto, the joint yoke in question is also subjected to the full transverse force in addition to the peripheral force. The joint yoke half particularly concerned is thereby deformed radially outwards away from the joint axis. As a result of this deformation the opposing axial bearing is relieved of stress, and a corresponding play arises. The play in the cardan shaft not only reduces the quietness of running of the cardan shaft and the service life of all bearings in the joint, but also impairs the quality of the rolled product when the cardan shaft is used in rolling mills.